Standard interconnects are a critical component of developing a standard product line and off-the shelf hardware. The development of standard interconnects enables shorter electronics development cycles and lower electronics costs by enabling higher reuse. The challenge in the development of a standard physical implementation of inter-module/slice interfaces is the wiring of point-to-point inputs and outputs (I/O). Historical implementations of point-to-point connections are generally either a unique backplane interconnect with a standard connector I/O configuration for each microelectronic module (e.g., card or circuit board) in a microelectronic assembly or unique connector I/O configuration for each microelectronic module in a microelectronic assembly with a standard backplane interconnect. Development of the unique hardware increases cost and the development schedule.
Signals within a microelectronic assembly are traditionally routed from one printed wiring board to another through the use of a backplane. The backplane approach requires the design of an additional circuit board. This additional circuit board, or backplane, is a disadvantage to the unit for several reasons. The backplane must be redesigned when signals between printed wiring boards change or when new printed wiring boards are added to the microelectronic assembly. This can be costly and time consuming, especially if the change is made late in development.
In addition, the backplane limits the mechanical construction of the microelectronic assembly as the backplane needs to be placed perpendicular to the other printed wiring boards. Printed wiring boards must be put into a solid housing instead of being connected as slices, where each board has its own metal housing on the edge and the individual slice housings bolted together form the unit housing. Using a backplane means that the mechanical construction of the assembly must be redesigned when boards are added to the assembly because the housing is one solid metal structure. The requirement of a backplane also results in a larger size and weight for the assembly than would be necessary if the assembly housing was limited to the length and width of the printed wiring boards instead of having to be long enough to account for an additional perpendicular board. In addition, connecting to the backplane from a circuit card requires an additional connector within the signal path, which often causes signal degradation due to poor impedance control. Backplane connectors which guard against signal degradation can be expensive. The added connector, connections, and signal path length are a reliability liability. In addition, testing of individual boards within an assembly without the backplane can present challenges.
A need therefore exists for improved microelectronic assemblies and methods for interconnecting microelectronic modules.